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Design Quirks are an optional rule set, first formalized in Strategic Operations. They are intended to increase the depth of gameplay, providing rules for otherwise-unsupported features mentioned in game fiction. The idea is an old one, first established in the 'Mech descriptions in the original versions of TRO:3025. The Javelin's entry, for example, contained rules for an early version of the Unbalanced Negative Quirk[1].

Currently, relatively few BattleMechs have canonical quirks; Strategic Operations assigns (often incomplete) sample quirks to a handful of units from TRO: 3039. Volumes of the PDF-only Experimental Technical Readout series published during or after July 2011 (starting with XTR: Clans) include quirks for most units. TRO: Prototypes first collected these. In addition, the TROs of the 3145 series gave quirks for all the units they presented. Several new Quirks were introduced in these sources, which are compiled (along with the TRO: Prototypes quirks) in the print version of TRO: 3145 and RS:3145,NTNU. Interstellar Operations added several items of Era-dependent equipment that grant one or more Design Quirks, rules for Quirks in Strategic Battleforce[2], and (with the Alpha Strike Companion[3]) clarified which Design Quirks apply to Drone units [4]

In keeping with the more-abstract nature of the Alpha Strike and Strategic Battleforce rulesets, the Quirk restrictions and rules in the Alpha Strike Companion and SBF are generally streamlined [5][4], and often very different than the BattleTech rules. The rules for these games are presented below if the points cost or game rules differ significantly. Some quirks are removed from both rulesets, with Strategic Battleforce having the fewest Quirks and BattleTech the most.

Note that Quirks lack conventional balancing mechanisms, such as Battle Value. Strategic Operations merely encourages designers to balance positive quirks with negative ones of equal or greater value, though some canon designs do not. Both Strategic Battleforce[2] and Alpha Strike[5] now require player-generated units to balance Quirk points, though some Quirks are irrelevant to battlefield performance and introduce possible imbalances to "one-off" games.

The Accurate Weapon Quirk marks a weapon or weapons bay as having exceptional design or construction quality. As such, it receives a bonus to the target numbers for to-hit rolls. While this Quirk can be applied to multiple weapons or weapon bays on the same unit, the cost of the Quirk must be paid for each[9].

Points: Variable; proportional to the damage potential of the weapon or weapon bay.

Units with the Anti-Aircraft Targeting Quirk have an advanced targeting system that allows them to make more accurate attacks against flying units. VTOLs, WiGE, conventional fighters, AeroSpace Fighters, Fixed-Wing Support Vehicles and DropShips all count as flying units, as do units engaged in a combat drop.[9]

Points: Variable; proportional to the damage potential of the unit's ranged weapons.

When operating inside the atmospheric envelope of a planet, AeroSpace units with the Atmsopheric Flyer Quirk receive a bonus to control rolls to reflect the exceptionally stable and highly maneuverable nature of the unit.[9]

Representing a tactical battle computer that offers more effective control of a combat force, the Battle Computer Quirk designates an advanced command unit. Having at least one in-play, with a conscious pilot or crew[11] grants a bonus to Initiative Rolls made by the unit's force. This modifier is not cumulative with that granted by the presence of a Command BattleMech.[9].

The BattleMech has been designed as a command unit. If one or more Command units is present on the battlefield, with a conscious MechWarrior[11], their force receives a small bonus to its Initiative Rolls. This modifier is not cumulative with the modifier granted by units with the Battle Computer Quirk.[9]

Compact 'Mechs are especially small and easy to transport. They take up half the normal space in a transport's 'Mechbay, though they will still take up a full Repair bay. Two Compact 'Mechs may be loaded into one standard Transport bay.

A Cowl Quirk represents reinforced armor, protective baffles, or other improved defenses around the cockpit of the BattleMech; it provides additional armor against attack from the sides and rear of the head.[9]

Units with the Distracting Quirk are designed or modified to intimidate opponents with their appearance. Such units impose a penalty to morale checks opponents must make when the Tactical Morale rules are in play, and are cumulative with the Demoralizer Special Piloting Ability[14]. Like other "psychological" Quirks and SPAs, the Distracting quirk does not apply to Drone and Robotic units[3][7].

Repair and replacement rolls made for a unit with the Easy to Maintain Quirk receive a bonus to the target number modifier to reflect the fact that the unit is easier to maintain and repair by design.[9]

Units with the Easy to Pilot Quirk are typically training units, designed to be used by the Greenest pilots, crews and MechWarriors. When piloted by someone with a Piloting Skill lower than Elite level a unit with the Easy to Pilot gives the operator a bonus to the target number modifier for most Piloting Skill rolls.[9]

Capable of twisting their torso sections much further than the average BattleMech. 'Mechs with the Extended Torso Twist Quirk can Torso Twist one hexside farther than normal. This Quirk can be applied to units which cannot normally Torso Twist.[16]

Alpha Strike:

The unit gains a 360-degree arc of fire, though it retains its Rear Arc for damage purposes.[15]

The Improved Cooling Jacket Quirk may be taken more than once by a unit; each iteration applies to a different weapon or weapons bay, and denotes the presence of an improved cooling mechanism that reduces the heat generated by the weapon or weapons bay when it fires. The cost for each iteration of the Quirk taken by the unit must be paid for separately.[16]

Units with the Improved Life Support Quirk offer a significant reduction in the apparent level of heat used for checking if the pilot or operator receives damage following a critical hit to the life support systems.[17]. They also double Life-Support endurance [18]

Equipped with an advanced sensor suite, Improved Sensors units count as having an Active Probe even if one is not equipped, and if an Active Probe is equipped, the effective range of that Active Probe is increased by the sensor suite.[17][15][7]. The specific range of the "free" Probe was altered by errata[11].

The Improved Targeting Quirks offer a bonus to all ranged to-hit numbers within one or more selected range brackets. A unit can take this Quirk more than once, with each iteration applying to a different range bracket[17], but the cost varies by the Range bracket selected [11]. Cannot be combined with Variable-Range Targeting, and does not apply to physical combat[15][7].

A unit with the Internal Bomb Bay Quirk may use internal cargo space as a bomb bay, although in BattleTech rules doing so is risky. Ground fire has a chance of striking through the bay doors and detonating any remaining ordnance within the bay while the unit is dropping bombs.[17][15][7]

An early branch of handheld weaponry tech, Jettison-Capable Weapons can be ejected in combat and later picked up and reattached.

A unit may carry up to two such weapons, although each must have this Quirk and pay for it separately, and some weapons (such as those mounted in pod space on Omni-platforms and handheld weapons) cannot take this quirk. A jettisoned weapon generally follows the rules for ejecting ammo, but does not explode. Jettisoned weapons may subsequently be reattached in much the same time as an ammunition reload, but unlike dropped handheld weapons, other units may not pick up and use a jettisoned weapon.[19]

The Modular Weapons Quirk offers two benefits to the unit that possesses it. While it does not offer the flexibility of an Omni-design, it takes half the usual time to replace weapons or install customizations. Despite these benefits, repairs performed in place still take the usual time.[17]

Whereas for most units attacking multiple targets in a single turn would result in a penalty being applied to various attack rolls, a unit with the Multi-Trac Quirk is capable of tracking multiple targets at once and can attack more than one target within the front and arm arcs without attracting a penalty. This bonus does not extend into the rear arc though, with targets in that arc still generating the secondary targets penalty.[17]

The unit's arms are mounted, like the Dasher's, to project above the 'Mech rather than hanging naturally. The 'Mech can fire its arm-mounted weapons over some obstacles, though this exposes it to hostile fire.[19]

Points: 2

Applicable to: BattleMechs and IndustrialMechs with at least one Arm-mounted weapon[19]

Alpha Strike:

As above, but only ignores 2" of Blocking Terrain. In addition, damage is halved, and the attack suffers a +2 penalty[21].

BattleMechs with the Protected Actuators Quirk benefit from increased joint protection or more rugged actuators; this imposes a penalty on both battle armor units and conventional infantry units attempting to make Leg or Swarm attacks against the BattleMech.[17]

BattleMechs with the Reinforced Legs Quirk have been designed to engage in physical attacks - particularly the Death From Above Attack - and as such suffer only half of the normal amount of damage for performing a DFA successfully.[17]

The majority of war machines, be they 'Mechs, vehicles or AeroSpace craft are built with a single seat in the cockpit. Some, however, are constructed with a simple second seat in their respective control areas, intended for use by passengers, observers, instructors and the like; this is reflected in the Rumble Seat Quirk. Rumble seats do not have access to the unit's controls, nor any ejection equipment (though they will eject as normal in a Combat Vehicle Escape Pod or Full-Head Ejection System), but the rumble seat may feature controls allowing the passenger to initiate an emergency shutdown of the unit - important in trainer designs.

The passenger in a rumble seat is vulnerable to the same damage from hits or rising heat levels as the pilot or operator, and rumble seats are not available in any unit that is from a light or ultralight weight class, uses a small cockpit, a torso-mounted cockpit, the Cramped Cockpit Design Quirk[19], a Torso-mounted Virtual Reality Piloting Pod (VRPP) [22], or an Interface Cockpit. [23]

Points: 0

Applicable to: Medium, Heavy, and Assault AeroSpace Fighters, BattleMechs, Combat Vehicles, Small Craft and Support Vehicles without Torso-Mounted, Cramped or Small Cockpits [19]

The Searchlight Quirk denotes that a unit has been fitted with a high-powered searchlight. While useful, this searchlight can be destroyed if the unit takes damage from particular directions[24]Strategic Operations, p. 196</ref>[21][7].

A relatively common adaptation, the Trailer Hitch Quirk allows one unit possessing the Quirk to tow a second unit that also possesses the same Quirk. Towing another vehicle via the Trailer Hitch Quirk is functionally the same as for Support Vehicles that possess the Tractor chassis modification, but only tracked and wheeled Combat vehicles may possess the Trailer Hitch Quirk[24][21][7].

The Variable Range Targeting Quirk is incompatible with the Improved Targeting Quirk. Units with the Variable Range Targeting Quirk incorporate an advanced targeting system that allows the unit to make more accurate attacks at certain ranges, although this benefit is offset by a corresponding penalty to other ranges. The unit with the Quirk must designate in the End Phase of each turn whether it wishes to receive the targeting bonus at short or long range. During the next turn, the unit receives a bonus to ranged attacks made at the range chosen the turn before, but a penalty to the opposite range - so, a bonus at long ranges means a penalty at short ranges, and vice versa[24].

Points: Variable, based on maximum damage output of unit's weapons and their ranges.

The VTOL Rotor Arrangement Quirk is only intended for use in games where the advanced vehicle movement rules from Tactical Operations are in effect. The presence of this Quirk indicates that the VTOL doesn't have the more common rotor arrangement of a single main rotor and a smaller tail-mounted stabilizing rotor. Instead, it has either dual rotors or co-axial rotors.[24]

A dual rotor arrangement mounts two rotors of equal size to the top of the airframe, either one in front of the other or side-by-side. The arrangement of the rotors makes no difference for purposes of recording damage, but alters the flight characteristics of the VTOL; the unit receives a bonus to the target numbers for all Piloting Skill Rolls, but suffers from a larger turn mode and is incapable of either sideslipping or performing bootlegger maneuvers.[24]

The co-axial rotor arrangement mounts both rotors on the same mast; the co-axial rotor arrangement lowers the stability of the VTOL but significantly increases the aircraft's maneuverability. Co-ax VTOLs receives no penalty to rolls on the Failed Maneuver Table, but any critical hit to the rotors imposes a penalty to all Piloting Skill Rolls.[24]

This Quirk indicates that the unit has a ballistic or missile weapons that is prone to jamming at unfortunate times. The unit must make another roll after each to-hit roll with the affected weapon system to see if the bay or system jams or, in extreme situations, explodes.[24]

Restricted to units with ammo-dependent weapons. Every time the unit fires these weapons, it must pass an additional 2d6 roll or its attack is cut by half the value of all its ammo-dependent specials (rounding up). Minimum damage does not apply[21]

A unit with the Bad Reputation quirk is perfectly sound and operable, but for some reason has earned a bad reputation. As a result, it is only worth half the normal resale value - although when purchasing such a unit, players in a game should pay full price.[24]

BattleMechs with this Quirk generate additional heat under certain circumstances. The player must make a dice roll to avoid generating additional heat for the rest of the game whenever a BattleMech falls, is forced to make a Piloting Skill Roll from taking damage, and receives or executes a physical attack.[24]

This Quirk subjects a unit to the same penalties as a Small Cockpit, but the actual weight and critical slots occupied by the cockpit are those of a standard cockpit[24]. It may not be applied to a unit with a Virtual-Reality Piloting Pod (VRPP)[22] or Interface Cockpit [23]

If the pilot of a unit with the Difficult Ejection Quirk is forced to eject, he or she must make a Piloting Skill Roll; if the roll is failed, that pilot suffers additional damage during the course of the ejection[24].

This Quirk indicates that the unit in question is harder to repair and maintain than the average unit of its kind. In-game, there is a penalty to the target number modifier for repair, salvage, and maintenance actions[29][28]. HarJel systems[30] and RISC super-cooled Myomer[31], automatically give a unit this Quirk.

This Quirk indicates that one of the energy weapons on the unit in question suffers from poor electromagnetic shielding, resulting in firing that weapon causing interference in other equipment on the unit. Affected electronic systems cannot function in the round after a weapon affected by the EM Interference Quirk fires. This includes: any Active Probe, Artemis IV or Artemis V Fire Control Systems, any form of C3 system, NARC, MASC, Cockpit Command Consoles, the Chameleon Light Polarization System, the Blue Shield system, any other Electronic Warfare equipment, Streak Launchers, the MRM Fire Control System, Null Signature Systems, Superchargers, the Void Signature System and any form of Stealth Armor[29]

Swarm and Leg attacks are more effective against units that suffer from having poorly-armored or exposed actuators; a unit with this particular Quirk is an easier target for enemy units conducting such attacks against the unit.[29][28]

The Exposed Weapon Linkage may only be taken once on a unit. It must be taken against one type of weapon, and applies to all weapons of that type[11]. The designated weapon suffers from being exposed or poorly armored, and when the location within which that weapon has been placed is struck by an enemy attack, the weapon in question has a chance of receiving a critical hit.[29]

The Fragile Fuel Tank Quirk causes an Aerospace unit which receives a critical unit against the fuel tank to have a greater than usual chance of exploding; vehicles with this Quirk that suffer any critical hit are also prone Fuel Tank criticals.[29]

The Hard to Pilot Quirk indicates that the pilots, crew or MechWarrior of the affected unit suffer a target number penalty for all Piloting or Driving Skill Rolls because the unit is inherently difficult to pilot[29]. It is automatically applied to all units with a Direct Neural Interface if the pilot lacks DNI implants [32], and to units whose pilot is using a "cyber-haunted" Advanced Neuro-helmet[20].

Note: Using a unit with the Illegal Design quirk requires the specific consent of all players.

Battletech:

This quirk allows the unit to break normal construction rules, but can disable it in combat.[33]

Illegal units give a penalty to repair or modification rolls. If the repair fails, the component will also gain the Nonfunctional quirk.

Units given the "Illegal" quirk must also be given the "Obsolete" quirk with the same year as their introduction.

Points rebate: None.
Applicable to: All units.
Alpha Strike:

As above, but the unit suffers doubled penalties for being Obsolete, can be automatically destroyed on a Repair roll of "2", and can never be replaced with an identical unit in a campaign[28]. It also costs 5x the normal rate[34].

This Quirk can be taken by a unit more than once, provided that it is applied to a different weapon or weapons bay each time. The affected weapon or bay is less accurate than normal, translating into a penalty to its to-hit rolls.[35]

While most 'Mechs mount their arms in "shoulder" position high on the torso, some sling the arms well below their centerline, near the hips. All arm-mounted weapons on the BattleMech are fired from one Level above the terrain, instead of two Levels as normal. In addition, the unit's Arms are covered by partial terrain or water as though they were Legs.

Applied to both 'Mechs with no arms and 'Mechs with arms that are completely ineffective at assisting a 'Mech regain its feet after a fall, this Quirk imposes a penalty on target numbers for Piloting Skill rolls made to stand up, although this modifier is not cumulative with advanced rules for standing up as presented in Tactical Operations. 'Mechs with this Quirk cannot make physical attacks or carry items using its arms for obvious reasons.[29]

Weapons marked as having this Quirk lack the standard cooling jacket normally applied to such weapons, and as such will generate more heat when fired compared to their correctly-cooled counterparts.[29]

Each iteration of the Obsolete Quirk is associated with a particular date. That date indicates when the unit with the Obsolete Quirk went out of production, and from that date onwards units of that type become increasingly difficult to maintain. Rolls to repair the unit, obtain replacement parts or even locate replacement parts become increasingly difficult for every fifteen years the unit has been out of production, and for every twenty years the unit has been out of production the resale price of that unit drops substantially. If a unit goes back into production at any point after becoming obsolete it takes a decade for the effects of the Obsolete Quirk to be negated.[37]

The Unit is much larger than normal, becoming an easier target. It also has difficulty moving through certain terrain without receiving damage, and cannot take cover as effectively as other units of its type. In Alpha Strike, Oversized units have more difficulty dropping troops as well[36].

Applicable To: Heavy and Assault 'Mechs and Combat Vehicles, and Medium-sized Support Vehicles. Incompatible with the Narrow/Low Profile Quirk.[38]

Points Rebate: 3
Strategic Battleforce:

The unit has a flat bonus for all enemy units to-hit. There are no other penalties.[26]

Units which suffer from the Poor Life Support Quirk have inferior life support systems. Whenever the pilot or MechWarrior of the equipment may take damage from excessive heat and a damaged Life Support system, the the quirk worsens the Heat level modifiers.[29] In addition, the Life Support system's operating time is halved [18]

The Poor Performance Quirk reflects a unit that is unable to accelerate to maximum speed quickly; as a result, any unit with this Quirk must spend one turn limited to moving at the unit's Cruising, Safe Thrust or Walking rating before being able to use up to its full movement allowance in the next turn.[39]

Units suffering from the Poor Sealing Quirk are more susceptible to leaks and failures in hostile environments as a result of imperfections within the design of its armor and internal structure. In any situation where the unit has to check for hull breaches and/or flooding the unit attracts a penalty to the roll, and even units that would not normally be susceptible to such rolls are forced to check because of this Quirk. In addition to having to check in each situation that generates such a roll, units with the Poor Sealing Quirk must also make an additional check the first time they enter a hostile environment, suffering potentially catastrophic damage if the roll is failed.[38][40].

Units with this Quirk suffer a penalty to any to-hit rolls made in the appropriate range bracket, as a result of poor targeting capabilities. The quirk can be taken up to three times, allowing a unit to theoretically possess the Poor Targeting Quirk for all three ranges - short, medium and long.[39][40][26]. The value of the Quirk was later increased [11]. It may not be combined with any Positive targeting Quirks.

Some manufacturers are sorely lacking in quality standards; as a result, equipment produced by such sources and cursed with the Poor Workmanship Quirk is one quality step lower than normal and any critical damage rolls against such units earn a bonus to reflect the increased chance of such units suffering damage.[39]

This Quirk represents the many issues associated with technological equipment which is still going through its development and shakedown process. Components on such platforms tend to be less resilient and lack redundancy compared to components from full manufacturing production lines. Units with the Prototype Quirk have a significantly increased chance of suffering Critical Hits as a result of rolls for critical damage[39][40][26].

A crude ammunition-feeding system prevents this unit from swapping the ammunition types fed to one or more weapons in combat. The owning player must select and use a single ammunition type for the unit before the game. In BattleTech, the quirk can be taken multiple times, with each affecting all weapons of one type on the unit. In Alpha Strike, all weapons lose the ability to choose ammo types. Often seen in conjunction with the Exposed Ammo Feed negative Quirk. [38][40].

Points Rebate: 2
Applicable to: Any unit with a Switchable "(S)" ballistic weapon system [38], or (in Alpha Strike) with any ammo-dependent Special Attack Ability.

BattleMechs with the Weak Legs Quirk were never designed to deal with the stresses associated with physical attacks, and as a result whenever a unit with the Weak Legs Quirk is kicked or makes a Death From Above attack that unit has a chance of suffering a critical hit, even if the leg armor isn't breached by the attack itself.[39]

An AeroSpace unit with the Weak Undercarriage Quirk has been constructed with a flimsy undercarriage that is prone to collapse if a unit makes a landing with a significant margin of failure against the required Piloting Skill Roll. If an undercarriage collapse occurs the unit takes significant damage and the undercarriage gear is destroyed.[39]